In general, it is preferable that a sliding surface has a smooth surface to reduce friction in the sliding surface. However, if the sliding surface is the smooth surface, a friction resistance can be lower but some level of heat is generated at the sliding surface so that there is a possibility that an adhesion occurs in accordance with so-called seizing. Therefore, it is required that the sliding surface has any proper surface roughness.
In the past, forming a concave portion by applying shot-blasting to the sliding surface is a well-known technology. A technology is known to form an oil reservoir on the sliding surface of the sliding member by the shot-blasting treatment (refer to, for example, Patent Document 1).
Patent Document 1: Japanese Patent No. 4848821